One of the most difficult problems encountered in the design, construction and operation of semiconductor devices is the constant bombardment of the device with natural high-energy particles. A variety of radiation, including alpha particles, gamma rays and high-energy ions, constantly bombard the surface of the earth and are found in far greater numbers in outer space. These particles can be extremely destructive in the microscopic context of a semiconductor device. As high-energy particles or ions pass through a semiconductor layer, they leave in their wake a trail of electron-hole pairs. These electron-hole pairs constitute a source of stray carriers. If they are present in the wrong spot in a circuit at the wrong time, they can cause errors in such devices as memory cells, latches, and other logic circuits. These errors are known as single-event upsets or SEUs.
To prevent single event upsets, conventional resistors are usually added to a circuit to slow the propagation of voltage change caused by the collection of the stray carriers through the addition of an RC delay factor. However, these resistors also slow all other carriers in the device and thereby slow its operating speed. This is especially apparent in memory devices where access time ("READ" time) and programming time ("WRITE" time) of the memory component are two of the chief limiting factors to the speed of operation of an integrated electronic system.
Therefore, a need exists for a method and apparatus for protecting semiconductor devices from single event upsets which do not slow the normal operation of the device.